


Sans' Gift

by SoloShikigami



Category: Undertale (Video Game)
Genre: Incest, M/M, Multi, Sibling Incest, Threesome, Threesome - M/M/M, Underfell Papyrus, Underfell Papyrus/Sans, Underfell Sans, Underswap Papyrus, Underswap Papyrus/Sans
Language: English
Status: Completed
Published: 2016-11-18
Updated: 2016-11-18
Packaged: 2018-08-31 17:02:45
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 4,146
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/8586643
Author URL: https://archiveofourown.org/users/SoloShikigami/pseuds/SoloShikigami
Summary: Sans absolutely hated his birthday. This was a fact that Papyrus had been very well aware of since Sans was a teenager. He didn't really know what happened; celebrations were few and far between in the Underground, but birthdays were something to be admired because it marked surviving another year in their violent world.But this year, Papyrus figures out something that Sans really wants and he's sure he would never go after it himself, so swallowing his pride he arrnages a birthday surprise that Sans won't ever forget.





	

**Author's Note:**

  * For [PurrfecktlySinful](https://archiveofourown.org/users/PurrfecktlySinful/gifts).



> ... and speaking of birthdays, this fic was a gift for my amazing friend PurrfecktlySinfull! Please go check out her [Tumblr ](https://purrfecktlysinful.tumblr.com/) and her [Ao3 ](http://archiveofourown.org/users/PurrfecktlySinful/pseuds/PurrfecktlySinful) for some awesome fics and more!

            Sans absolutely hated his birthday. This was a fact that Papyrus had been very well aware of since Sans was a teenager. He didn't really know what happened; granted, celebrations were few and far between in the Underground, but birthdays were something to be admired because it marked surviving another year in their violent world.

            Papyrus had pleaded in his younger days for Sans to allow something special on that day, and he would always find a way to change the subject or would just ignore him.

            Papyrus hated being ignored.

            But the taller skeleton came to a new realization as to why his brother despised discussing a day where he would be the center of attention - he hated himself. Papyrus had been painfully aware that his brother suffered from an unbelievable lack in self-esteem, and while he knew he wasn't wholly responsible, he did take some of the blame and made fixing it one of his top priorities.

            Living on the surface and their romantic relationship seemed to help quite a bit in that area; Sans was finding it more and more difficult to believe the voices that told him how worthless he was when someone as amazing as Papyrus made him feel things he could never bring about on his own. Papyrus was always finding new ways to show Sans how wonderful he was in his own right, and it continued to keep things exciting between them.

            But it still wasn't enough to keep Sans from snarling at him when he asked.

            "So, next week," Papyrus started the conversation, or at least tried.

            "Please, don't," Sans had responded.

            Papyrus sighed, not really in the mood for this. "Sans, you are being absolutely ridiculous and unreasonable! I insist that this year-"

            Sans growled and stood from the table, making it shake and spilling milk from Papyrus' glass.

            "Drop it, Boss," Sans snarled before leaving the kitchen in a huff.

            ' _Well, at least he has the self-esteem to stand up to me like that,_ ' Papyrus thought sourly.

            Luckily, he could guess where his brother was going; another thing that had been aiding their recovery from their world of kill or be killed was the ability to dimension-hop to the other universes. Another sign of Sans' slow rebuilding of his self-worth was his even-slower budding of affection for the Papyrus of the Underswap universe. He kept most of his thoughts to himself, but Papyrus knew his brother and noticed the lingering gazes, the amount of time he spent with the other, the way a very faint dusting of red was on his cheekbones whenever the other skeleton came up in conversation. At first, Papyrus had been quite upset, but after speaking with some of the others (and finding there were other cross-attractions among them), as long as he was Sans' number one, everything was fine.

            "So, your bro really hates his birthday," Swap said when Papyrus paid him a visit a few days after the outburst at breakfast.

            "I am well aware," Papyrus replied. "Sans doesn't particularly like himself, so he feels something like a birthday is too good for him."

            "Gee, wonder where he got that idea."

            Papyrus bristled; he knew Sans would likely speak about their darker days when they fought more and Papyrus was borderline merciless with his insults, failing to realize that while _he_ could brush such things off, it wasn't so easy for Sans, and he really needed his brother to be more sensitive to that. The fact that Swap was unhappy with him on this matter only served to help him further in his quest.

            "While Sans is free to tell you what he likes, I have no time to stand here defending myself. Unlike your lazy ass, I have a schedule to keep."

            "All right, all right," Swap took the toothpick he had been chewing on out of his mouth. "What do you want?"

            A slow grin spread across Papyrus' teeth. "If you are concerned with my brother's level of self-esteem, I wondered if perhaps you would be willing to aide me in giving him a birthday gift that will help boost it, or at the very least, give him a birthday he won’t soon forget."

            Swap could read the grin and was piqued at the tone the other skeleton was using.

            "I'm listening..."

~ * ~ * ~ * ~ * ~ * ~ * ~

            "Papyrus, what is this about?" Sans asked with an exasperated tone. "I mean, I'm all for kinky games and whatnot, but I'm a little _blindsided_ by this. Heh."

            Papyrus rolled his eyes. He was guiding the blindfolded Sans upstairs.

            "Enough of your stupid jokes and puns," Papyrus scolded, reaching past him for a moment to open the door. "Otherwise I'm not going to give you your birthday present."

            Sans' body stiffened for a moment before he sighed. "Papyrus, I appreciate the thought and all, but you know how I feel about that."

            Of course, Sans couldn't see the smirk being shared before he was shoved forward.

            "Oh, trust me, I think you'll like this one," Papyrus said.

            Sans tripped as he was forced over the threshold, his arms flailing as he prepared to fall. However, a pair of hands caught him under his arms

            "What the-?" Sans stammered.

            "Heh heh, you're pretty cute when you're all flustered and confused," a familiar drawl said as fingertips touched lightly across his jaw.

            "P-Papyrus?!" Sans said, feeling his face flushed with embarrassment as his feet scrambled to get his footing.

            "Relax, I got you, Red," he murmured, using the nickname he came to call this Sans.

            "Boss, what's this-?"

            Sans' question was cut off when he felt a tongue lick across his teeth just before the gentle _clack!_ of bone against bone as Swap leaned in to kiss him. Sans shuddered with desire; he always wondered what it would be like to kiss this laid-back version of his brother - well, he wondered about doing far more than that, but he was content to take what was being given.

            Papyrus had shut the door so quietly the other two took no notice. He watched for a moment as Swap lazily explored Sans' mouth, his orange tongue twining around Sans's bright red one. He wrapped one arm around Sans' back and pulled him in closer, his other hand still caressing his jaw, working up to the side of his face. Papyrus knew he would be all touchy-feely, and Sans seemed to like it so he let them be.

            After a little while, Papyrus cleared his throat. Swap glanced up at Papyrus, catching his gesture, and slowly broke off his and Sans' kiss. Sans was panting, his hands had moved up to grip the front of Swap's sweatshirt, and now he looked as if letting go would cause him physical harm.

            Swap chuckled and pet the top of Sans' head. "It's okay," he murmured in a soothing tone. "We're going to make you feel really special."

            Sans shuddered, swallowing, the words sounding both wonderful and terrifying at the same time.

            Papyrus came up behind him, wrapping his arms around his shoulders and pressing himself up against his back. He bent to drop a gentle kiss to the back of Sans' skull.

            "I always take good care of you, don't I?" Papyrus murmured against him, his hands began to trail up and down his rib cage just under his jacket.

            "Y-yes," Sans stuttered, shivering at the contact and gripping Swap's sweater even tighter.

            "Of course, we can stop if it's too much for you," Swap said gently, pressing a soft kiss on the side of his mouth. "I won't be upset."

            Sans didn't trust his voice at that moment so he shook his head.

            "Good," Swap said, glancing up at the other skeleton over Sans' shoulder.

            Papyrus had a pleased smile on his face as he peeled Sans' jacket off. He gave a nod to Swap, allowing the other skeleton to start moving his hands down to the hem of Sans' old t-shirt, pushing underneath it to trail his fingers up his spine and touch along his lower ribs. Papyrus rubbed along Sans's shoulders, pressing down his sternum, fingers tracing back up to almost tickle at his neck.

            The two drew soft whimpers from the smaller skeleton, making him squeeze his eyes shut despite the blindfold. Soon they had worked the t-shirt up and over his head and Papyrus made a small gesture at Swap. He nodded and reached up to slide the blindfold up over Sans' head. Sans blinked up at him, eyes readjusting to seeing again, but it didn't seem to matter as he closed his eyes under another deep kiss from Swap, tilting his head back a bit.

            Sans was dimly aware of Papyrus circling his arms around his waist, too absorbed in the tongue that explored his mouth, licking at the roof of it, sharing his taste of nicotine and honey.

            "Ah!" Sans gasped. He was sharply pulled back into reality when the swatch of fabric that was used to block his vision yanked at his neck, pulling him back suddenly. He was still too dazed to do more than stare dumbly up at his brother, his eyes questioning laced with apprehension.

            Papyrus simply smiled down at him, pulling the fabric away and letting it drop to the floor before looking up at Swap. "I think we should make Sans a little more comfortable to receive his gift."

            "I think that's a good idea, poor guy looks about ready to collapse," Swap said, giving Sans a kind, almost indulgent smile.

            "Like I care what you think. Take off his pants and sneakers," Papyrus ordered.

            "Heh, yes, sir."

            Papyrus' eyes narrowed at the too-playful tone; it bordered on disrespectful in his book. As the other bent to start carefully undressing the rest of Sans, Papyrus kept busy dragging his sharp fingertips across his ribcage again, harder this time, and nibbling on his neck with his sharpened fangs.

            "Enjoying yourself, Sans?" Papyrus purred in his ear as Swap took off his socks after removing the beaten-up sneakers.

            "I am," Sans murmured, taking in a sharp breath when Swap lifted a now naked foot to kiss the instep.

            "Good. I want you to take a good look at him, Sans."

            Sans found it a little weird, but he did as he was told and he looked down at Swap, who was absorbed in his task of undressing him.

            "He is doing this quite on his own, I must tell you," Papyrus said with a touch of something akin to fondness is his voice. "He was very eager to do this for you; he is most certainly not here for my sake."

            Another shudder passed over Sans as Swap looked up at him with his smile as he rubbed the back of his tibia as he slipped off the other shoe. Their eyes met again, and while Sans was a little lacking when it came to reading people, the dedication and caring on Swap's face was quite clear.

            "He is taking my directions quite well," Papyrus continued, speaking of Swap as one would discuss a dog. "A few simple ones, because after all, I do know want you like best."

            Sans felt rather than heard the soft laugh from Swap, his breath ghosting over his femur as he dragged his shorts down his legs, dropping a kiss on his patella as he lifted one foot again to pull the shorts completely away.

            "I still have creative license," Swap murmured, nipping gently at his other femur and he finished taking the shorts off. "Edge Lord may have told me where to touch you, but I get to decide how."

            Another wave of shudders and a small moan came from exhaling the breath Sans didn't know he was holding and he took notice that Papyrus had wrapped his arms rather firmly around his ribcage. He was about to ask why, but a warm, wet tongue slid across the inside of his pubic arch, making him cry out and his knees went weak.

            Papyrus tightened his hold slightly and Swap put his hands on the back of his hipbones to help keep him steady, but he continued his task without letting up.

            Sans panted, squirmed, and moaned under the touches, pressing himself back into Papyrus while trying to move forward into Swap, relishing the tingle left on his bones when he moved to a different area.

            "Mm, such a good boy," Papyrus murmured, his own hands wandering now and then as he watched Swap work. He also watched as red magic started moving from Sans' center, pooling into his pelvis and taking form.

            Swap leaned back as the magic began to solidify, marveling at the motions of the red swirls, how it moved from intangibility into solid mass; he figured it was likely the small bit of scientist within him.

            Once the beginnings of Sans' cock began to form, Swap reached out with his tongue to trace its outline. Sans whimpered at the contact - newly formed magic was always highly sensitive at first. He reached down to touch Swap, but Papyrus pulled his arms behind him, holding them captive with one hand.

            "No need, he knows what you would want," Papyrus murmured.

            Swap took the entire forming length into his mouth, his tongue wrapping around the shaft, squeezing it as he pulled back, his teeth nipped lightly at the head before taking him in again.

            There was no particular rhythm, no rhyme or reason to when his teeth touched, when he would lick along the sides or swallow him whole. It kept Sans off-balance, making the smaller skeleton squirm in his brother's grasp.

            "Beautiful," Papyrus murmured. "Watching your dick move in and out of that mouth; you're so thick, he almost has a hard time with it."

            Swap wanted to give him a look; Sans was well endowed, but nothing he couldn't handle, and he proved it by taking him in whole and swallowing around him.

            "Fuck, fuck, shit, wha- fuck!" Sans nearly screamed, more surprised by the move than anything.

            "Hmm, maybe it is about time," Papyrus murmured, using one hand to stroke down the back of his spine, curving around the bit of flesh his magic created on the back of his pelvis, fingers searching and finding an entrance.

            Sans gasped when he felt Papyrus' finger pressing into him, his magic rushing to make the intrusion a little less uncomfortable. A few thrusts and a second finger was pushed inside and Sans nearly double over with a groan.

            "Mmm, that's it, you are so amazing," Papyrus murmured, pumping his finger slowly inside of him. "The way you shudder and squirm, those delicious sounds coming from your perfect mouth, I could just eat you up."

            Papyrus bent to bite Sans' neck, a little rougher than any of the other attentions he gave him, nearly purring at the whimper that resulted as well as the slight indents in his bones.

            "I'm so lucky that you allow me to have you," Papyrus murmured.

            "Please, please," Sans begged, barely able to handle both of them like this.

            "Yes, yes, I did promise to make you a bit more comfortable," Papyrus said. "Game pause."

            Sans recognized it as a safe word, for the moment the words left Papyrus' mouth, Swap stopped and pulled away immediately. Sans nearly bit his tongue to keep from moaning at the look on Swap's face; he was disappointed at being told to stop, his eyes still spoke of a hunger that hadn't be satiated yet, and he looked eagerly past Sans' shoulder at Papyrus for his next instruction.

            Whatever the instruction was, it was given nonverbally; Sans was spun around to face his brother, his arms released, as Papyrus bent down to kiss him. The kiss was too brief.

            "Beautiful," Papyrus murmured, running the back of his hand down Sans' cheekbone. "Come along."

            Papyrus turned and started walking towards his bed. A pair of hands on Sans' shoulders guided him forward.

            "Are you having fun, Birthday Boy?" Swap said teasingly.

            Sans nodded.

            "I hope so. I wanted the chance to do this."

            Before Sans could ask for any sort of clarification, Swap’s hand were between his legs, touching him gently.

            Too gently.

            But before he could protest or comment, his arms were grabbed and he was yanked forward, sprawling over Papyrus' chest as he laid back on the pillows which he must have had set up earlier in the day. It allowed him to lounge comfortably, holding Sans to him.

            Sans felt a slight annoyance; he was hard as a rock, though slowly retreating from the edge that Swap had brought him to. Before he could vocalize his frustration, Papyrus shifted a little underneath him, moving a hand between them to stroke - no, he didn't stroke his cock, he was adjusting it. Papyrus adjusted it so it lay heavy and throbbing against something warm and wet.

            "What the-?"

            Sans tried to look down, Papyrus was certainly not wearing his pants, but Papyrus caught his chin in his hands and lifted his face to him.

            "Nevermind that," he murmured.

            Papyrus glanced over Sans’ shoulder so quickly that he didn't even notice. He _did_ take notice when a hand rested on his ass and he knew Swap's cock was brushing across his entrance.

            Sans’ hands gripped at Papyrus' chest, looking up at him in almost a panic. Was this really happening? Was he really allowing this? Allowing another monster to fuck him?

            "You know what to say if you don't want this," Papyrus whispered to him.

            "W-wha- y-you," Sans could just barely stammer as the head of Swap's dick breached him.

            "I know you want it, though," Papyrus murmured, his hand still holding Sans' chin so he couldn't look away. "My beautiful brother deserves to have what he wants on his birthday."

            Again, Sans wanted to answer, to say _something_ , but his words were lost in a wail as Swap sank into him, slowly and steadily. Sans panted, gripping Papyrus tightly, feeling every inch as Swap drove in to the hilt. He was thankful that Swap paused, relishing in the feeling of pleasing Sans, giving him a moment to adjust.

            "Such a beautiful expression," Papyrus said fondly, brushing his fingertips across Sans' forehead.

            Sans let out soft little whimpers and cries as Swap gave him slow, shallow thrusts, barely moving but it was enough for Sans to feel him. Swap hummed pleasurably.

            "You feel so good," Swap murmured, bending over to drop a kiss on the back of his head, then in the back of his neck, and on his shoulders. "You're so wonderful, Sans."

            Sans tightened around him at the sound of his given name being spoken with that voice.

            "P-Papyrus," Sans moaned, burying his face in his chest. "I-it's too much... I'm... Stars, I don't even..."

            Swap looked up at Papyrus questioningly at the almost senseless babbling. Papyrus subtly shook his head and gave him a smirk, reminding him that he knew damn good and well what he was doing.

            "Say the word and it stops," Papyrus reminded him. "All you have to do is tell us what you want."

            Swap had stopped moving, making Sans wriggle in desperation, so Swap put his hands firmly on his hips to get him to stop.

            "I, I d-don't know," Sans moaned. "Don't know w-what I want, Papyrus."

            He looked up at his brother with a pleading expression. Papyrus chuckled, caressing his face.

            "Luckily, I do know what you want."

            Papyrus leaned down to kiss Sans possessively. He broke away after a moment, licking his teeth and glancing up at Swap with a wicked smile.

            "Wreck him."

            Sans' eyes widened, he gasped when Swap pulled out, then screamed when he was penetrated again. Swap set a vigorous pace, Sans was surprised that he was capable of moving like that, or at least he would be, if all coherent thought hadn't been driven from him.

            "You are so cute like this," Papyrus murmured as he held him, feeling the force of every thrust. "I love the look on your face when you're being fucked senseless. Your eyes sparkle, your face takes on quite the fetching shade of pink, fuck, Sans, I hope you understand how lovely you look."

            "Pa-Papyrus," Sans whined, unsure which one he was calling out for. Maybe both of them.

            "Mmm, does it feel good for you?"

            Sans was barely able to contort his face into a look that clearly said " _are you fucking kidding me?_ "

            "Nyeh, heh, heh, yeah, it feels good for me, too. Having your dick sliding across my pussy like that, you feel how hot and wet it's getting?"

            Sans knew very well, but he couldn't answer; hell, he was summoning up every bit of focus he could to understand the words, and even then he could feel his logical senses slipping, slowly being replaced with nothing but pure, raw, carnal desire.

            "I love watching you like this; I can feel your soul pounding behind your ribcage, I love the feel of you against me," Papyrus' head was beginning to swim a little as well, what with his clit being stimulated by the thrusting of Sans' cock against it. He grunted a bit, canting his hips up. "Stars, Sans, I hope you know how much I love you, how wonderful you are."

            Swap didn't realize how turned on he would be at the whole experience; something about watching Papyrus holding Sans, speaking to him so sweetly, it reminded him of his own brother... His body flushed at the thought, then he was brought back to reality by a sharp wail from the Sans he was currently thrusting into.

            Papyrus smiled, petting his skull; he knew what that sound meant.

            "It's okay, Sans, let go, it's okay," Papyrus murmured gently.

            Swap stilled deep inside of Sans as his body clenched around him, his inner walls fluttering around him, Papyrus groaned as warmth spread over his mound as Sans came. Swap gasped, holding himself in tight control, looking down pleadingly at Papyrus.

            "Your turn," Papyrus said, petting Sans as he eased him down from his orgasm.

            Swap nodded, thrusting a few more times into Sans before pulling out and stroking himself to his climax, spurting pale orange magic across Sans' backside.

            The room was full of the sounds of their breaths catching and Papyrus murmuring sweetly to Sans. Swap smiled down at the two for a moment, and he didn't care if it would piss off Papyrus, he leaned over Sans and kissed the back of his head.

            "Happy Birthday, Sans," he murmured.

            Sans sighed happily in response.

            "You did well, he can't speak for a few more minutes," Papyrus murmured. "Mind cleaning him up?"

            "Sure," Swap said.

            "There should be a towel folded near the bed."

            Swap found it easily and gently wiped Sans's backside, bending down to kiss the slowly evaporating magic and his spine. Once he seemed clean, Swap wrapped the towel up and set it aside.

            "Good, now get in here."

            Swap blinked.

            Sans looked over his shoulder at the other skeleton. "Yeah, he's inviting you into bed for post-sex cuddling," he murmured with a lazy smile. "Please?"

            Swap smiled back. "Anything for the Birthday Boy."

            Papyrus moved himself and Sans over, making more than enough room for Swap. Papyrus sat up briefly to pull off his shirt and Swap followed suit, completely undressing himself before climbing into the bed behind Sans.

            Papyrus covered them with the blanket and pulled Sans closer. He looked over at Swap and gestured for him to move in close for a cuddle, and Swap did, snuggling up behind Sans and draping an arm over his middle.

            Sans sighed happily, one hand resting on Papyrus' sternum and the other reached behind and draped over Swap's hipbone.

            "Happy Birthday, Sans," Papyrus whispered, kissing his forehead. "Did you enjoy your gift?"

            "I did, very much, thank you," Sans murmured. "Is it a gift I can have more than once?"

            Swap felt Sans squeezing his hip and he subtly tightened the arm around him in return as he looked over at Papyrus.

            The other skeleton looked at Swap, considering for a moment before nodding.

            "That is acceptable. He made you happy and he will continue to do so," Papyrus said. The command in the last part was unmistakable.

            Sans smiled, leaning up to kiss him briefly before he rolled over and pulled Swap into a deep kiss. Swap kissed back eagerly and Sans smiled at him as he backed away.

            "You both made this the best birthday I ever had, thank you," Sans said, rolling onto his back, each hand grabbing one hand of the skeletons on either side of him and quickly drifted off to sleep.

            The taller skeletons smiled at the small one between them, curling up at his sides, and soon followed his lead.


End file.
